360 is making some odd noise (not disc related)

On the lower/right half of the console (depending on how you look at it, it's the part with the power button), today it has an odd rumble-like noise. It sounds sort of like the fan is blowing too fast, or something around the fan is slightly out of alignment, causing it to do a rumbling sound.

This happens whether there's a disc in or not, and starts within 10 seconds of turning it on. Just started today, although I remember it happening once before, several months ago, and I forget what I did (if anything) to stop it.

It's almost certainly the fan, but does anyone have any ideas for what to do?

EDIT: Ok, it went away after leaving the 360 sitting on the dashboard for a few minutes. I'm guessing something was slightly ajar with the fan or something and it (probably) corrected itself. Still would like a more concrete answer if anyone else has had this issue before.

---Eclipsing power is, at times, not only the instrument of demons, but also of gods.Lost, but not forgotten.

I would bet that your 360 is filled with dust. Mine used to do that until it expired :(---Height has nothing to do with skin colour, but I know this girl that tans alot that is short...yeah get your brain looked it, someone needs to fix it- DemonDog

my system makes a rumbling noise if I go to dashboard with a game in the system, but don't play the game. Once I start the game, it goes away. It also has a constant pulsating noise from the fans (Like they spin up and slow down constantly)---Ron Paul 2012